Search Publications
Approximating the X-ray spectrum emitted from astrophysical charge exchange
Smith, R. K.; Foster, A. R.; Brickhouse, N. S.
Charge exchange (CX), both onto ions in the solar wind and potentially in other astrophysical contexts, can create X-ray emission lines largely indistinguishable from those created in collisional or photoionized plasmas. The prime distinguishing characteristic is in the distinctly different line ratios generated by the CX process. A complete astro…
Measuring the solar meridional flow from perturbations of eigenfunctions of global oscillations
Roth, M.; Schad, A.; Timmer, J.
We present a new concept to infer the meridional flow in the deep solar interior from global oscillation data. This concept is based on the estimation of the coupling strengths of p-mode eigenfunctions mediated by the meridional flow. We illustrate the performance of the method using simulations and present first inversion results of a large-scale…
A magnetic cycle of τ Bootis? The coronal and chromospheric view
Schmitt, J. H. M. M.; Günther, H. M.; Poppenhaeger, K.
τ Bootis is a late F-type main sequence star orbited by a Hot Jupiter. During the last years spectropolarimetric observations led to the hypothesis that this star may host a global magnetic field that switches its polarity once per year, indicating a very short activity cycle of only one year duration. In our ongoing observational campaign, we hav…
Preliminary results on γ Dor and δ Sct-γ Dor hybrid s in the CoRoT exo-field of LRa01
Hareter, M.
The 131 days long, high-precision light curves observed in the CoRoT exo-field during LRa01 were investigated for γ Dor and δ Sct-γ Dor hybrid stars. In total 418 γ Dor and 274 δ Sct-γ Dor hybrid candidates were identified. For a fraction of these candidates spectra are available obtained at the Anglo-Australian Observatory. Effective temperatures…
Spectroscopic evidence of charge exchange X-ray emission from galaxies
Wang, Q. D.; Liu, J.
What are the origins of the soft X-ray line emission from non-AGN galaxies? XMM-Newton RGS spectra of nearby non-AGN galaxies (including starforming ones: M82, NGC 253, M51, M83, M61, NGC 4631, M94, NGC 2903, and the Antennae galaxies, as well as the inner bulge of M31) have been analyzed. In particular, the K\alpha triplet of O VII shows that the…
Debris disks as seen by Herschel/DUNES
Magain, P.; Krivov, A. V.; Eiroa, C. +18 more
The far-infrared excesses produced by debris disks are common features of stellar systems. These disks are thought to contain solids ranging from micron-sized dust to planetesimals. Naturally, their formation and evolution are linked to those of potential planets. With this motivation, the Herschel open time key programme DUNES (DUst around NEarby…
CSS091109:035759+102943: A candidate polar
Schwope, A. D.; Thinius, B.
We report optical time-resolved photometry of the CRTS transient CSS091109:035759+102943. Pronounced orbital variability with a 114 min period, large X-ray variability and the IR to X-ray spectral energy distribution suggest a classification as a magnetic cataclysmic binary, a likely AM Herculis star or polar.
Exospheric solar wind charge exchange as seen by XMM-Newton
Read, A. M.; Carter, J. A.; Semba, S.
We review a selection of recent papers describing solar wind charge exchange emission occurring in the Earth's exosphere as seen by the X-ray observatory XMM-Newton. We discuss the detection of this emission, the occurrence with respect to the solar cycle and solar activity, and various spectral signatures observed. We also describe a model develo…
Ion-ion charge exchange and X-rays from the winds of hot stars
Pollock, A. M. T.
Charge exchange occurs between charged ions with enough energy to overcome Coulomb repulsion, a condition satisfied for collisions at velocities like those of the winds driven from hot stars by radiation pressure. X-ray line ratios in some hot stars are inconsistent with those expected from thermal plasmas excited by electron impact. Ion-ion inter…
On the soft X-ray emission of M82
Mao, S.; Wang, Q. D.; Liu, J.
We present a spatial analysis of the soft X-ray and Hα emissions from the outflow of the starburst galaxy M82. We find that the two emissions are tightly correlated on various scales. The O VII triplet of M82, as resolved by X-ray grating observations of XMM-Newton, is dominated by the forbidden line, inconsistent with the thermal prediction. The …